Radiation imagery chemistry: process – composition – or product th – Radiation sensitive product – Silver compound sensitizer containing
Reexamination Certificate
2002-09-24
2004-01-27
Le, Hoa Van (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Radiation sensitive product
Silver compound sensitizer containing
Reexamination Certificate
active
06682882
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a production process of a silver halide emulsion, more specifically, the present invention relates to a production process of a thinner tabular grain emulsion.
BACKGROUND OF THE INVENTION
Tabular silver halide grains having a large light-receiving area are widely used as a photosensitive element. For increasing the light-receiving efficiency of the tabular silver halide grain, the smaller grain thickness is more preferred. The preparation of silver halide grains comprises two main steps of nucleation for forming grains working out to nuclei for growth, and grain growth. For the nucleation, a method of directly adding a water-soluble silver solution and an aqueous alkali halide solution to a reactor having a stirring unit of various types is used. However, the grains as nuclei in the course of growth pass through a high supersaturation region in the vicinity of a port for adding silver ion or halide ion and this causes a harmful effect that the tabular grains are increased in thickness. To overcome this problem, JP-A-10-43570 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”) and JP-A-2000-338620 disclose a method of adding a water-soluble silver solution, an aqueous alkali halide solution and an aqueous dispersion medium solution to an outside mixing vessel different from the reactor of undertaking the growth, thereby continuously forming silver halide fine grains, adding the silver halide fine grains to the reactor, and growing the grains as nuclei while dissolving the silver halide fine grains. However, the methods disclosed cannot produce silver halide fine grains having a narrow distribution and are not satisfied for obtaining thinner tabular grains.
On the other hand, in the production of silver halide grains of a silver halide emulsion, the total of the amount of water containing a dispersion medium necessary for stirring, the amount of water-soluble silver solution, the amount of aqueous alkali halide solution and the amount of additives is designed to be lower than the maximum liquid amount of a reactor. In the case of increasing the production amount and elevating the productivity, the production amount per once operation can be increased by increasing the concentrations of water-soluble silver salt and aqueous alkali halide solution occupying the majority of the liquid amount. However, the concentrations of water-soluble silver solution and halide ion are appropriately determined to obtain intended silver halide grains and if these concentrations are increased, not only the grain size, grain shape and grain size distribution are changed but also the photographic properties such as fog, sensitivity and gradation are adversely affected. In order to eliminate these adverse effects, it is necessary to remove the added aqueous solutions together with unnecessary salts while not changing the concentrations of water-soluble silver solution and aqueous alkali halide solution added. For this purpose, a method of using dehydrating and desalting apparatuses during the growth is disclosed in U.S. Pat. Nos. 4,334,012 and 5,242,597, European Patents 795,455 and 843,206, JP-A-11-231449, JP-A-11-237703, JP-A-11-352618, JP-A-2000-56420, JP-A-2000-56421, JP-A-2000-66320, JP-A-2001-56518, JP-A-2001-59994 and JP-A-2001-100348. However, according to these methods, a water-soluble silver solution and an aqueous alkali halide solution are directly added to a reactor and thick tabular grains are disadvantageously produced.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a process for producing a tabular silver halide grain emulsion having high sensitivity and low fog and more reduced in the thickness.
In the present invention, silver halide fine grains which are continuously prepared and supplied can be made to have a monodisperse grain size distribution immediately before the addition and by using the silver halide fine grains, a tabular grain emulsion more reduced in thickness than in conventional techniques can be prepared.
The object of the present invention has been attained by the following (1) to (16):
(1) A process for producing a photosensitive silver halide emulsion comprising silver halide grains and a dispersion medium, the process comprising adding a water-soluble silver solution, an aqueous alkali halide solution and an aqueous solution of gelatin having a molecular weight of 5,000 to 30,000 or less to a mixing vessel different from a reactor for the production of emulsion to prepare silver halide fine grains, adding the silver halide fine grains to the reactor for the production of emulsion to grow silver halide grains, and ultrafiltering the silver halide grains during the addition of silver halide fine grains, wherein 50% or more of the entire projected area of the emulsion grains is occupied by silver halide tabular grains having an aspect ratio of 10 or more and a thickness of 0.15 &mgr;m or less.
(2) The process for producing a silver halide emulsion as described in (1), wherein the silver halide grains present in the reactor for the production of emulsion are ultrafiltered under variable temperature conditions before the addition of the silver halide fine grains.
(3) The process for producing a silver halide emulsion as described in (1) or (2), wherein the residence time of the water-soluble silver salt, aqueous alkali halide solution and aqueous gelatin solution in a mixing space of the mixing vessel is from 0.001 to 10 seconds.
(4) The process for producing a silver halide emulsion as described in any one of (1) to (3), wherein the mixing vessel comprises a stirring tank and at least two stirring blades in the stirring tank, an aqueous solution of water-soluble silver salt and an aqueous solution of water-soluble halide are supplied through supply ports provided in the stirring tank of the mixing vessel, the stirring state in mixing the aqueous solutions supplied is controlled by the stirring blades having no rotary shaft protruding through a wall of the stirring tank and disposed with a space at the positions facing each other in the stirring tank, and the silver halide fine grains produced after the completion of stirring treatment are discharged from the discharge port provided in the stirring tank.
(5) The process for producing a silver halide emulsion as described in any one of (1) to (4), wherein the average equivalent-circle diameter of the silver halide fine grains is 40% or more of the number average thickness of the silver halide tabular grains under growing.
(6) The process for producing a silver halide emulsion as described in any one of (1) to (5), wherein the coefficient of variation in the equivalent-circle diameter of the silver halide fine grains is 30% or less.
(7) The process for producing a silver halide emulsion as described in any one of (1) to (6), wherein 50% or more of the entire projected area is occupied by grains having an equivalent-circle diameter of 3.0 &mgr;m or more.
(8) The process for producing a silver halide emulsion as described in any one of (1) to (7), wherein 70% or more of the entire projected area is occupied by hexagonal tabular grains having an epitaxial projection part at least at one apex.
(9) The process for producing a silver halide emulsion as described in any one of (1) to (8), wherein the emulsion is produced through nucleation, ripening and growth steps and the total silver concentration in the silver halide emulsion at the start of ripening step is from 0.0015 to 0.15 mass %.
(10) The process for producing a silver halide emulsion as described in any one of (1) to (9), wherein the reactor temperature in the nucleation step of adding an aqueous silver solution and an aqueous halide solution is 5° C. or less.
(11) A process for producing a silver halide emulsion through nucleation, ripening and growth steps, the silver halide emulsion being a photosensitive silver halide emulsion comprising silver halide grains and a dispersion medium, wherein 50% or more of the entire projected area of grains
Ihama Mikio
Ikari Shinji
Mitsui Tetsuro
Nakatsugawa Haruyasu
Takahashi Kazutaka
Fuji Photo Film Co. , Ltd.
Le Hoa Van
Sughrue & Mion, PLLC
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